This invention relates to a cushion bearing of the type used in motor vehicles combining a bearing block of resilient material and a gas spring.
German Offenlegungsschrift No. 3,505,632 discloses a cushion bearing combining a resilient rubber bearing block and a double-acting gas spring, i.e., one acting in either of the two possible directions of opposite relative movement between two opposed bearing seats. That combination provides highly desirable properties in that it will both suppress propagation of small-amplitude high-frequency vibrations such as engine noise and absorb higher-amplitude low-frequency vibrations such as motions resulting from alternating load impacts. In other words, such a combination bearing is very soft for small-amplitude motions at high frequency, yet hard for large-amplitude motions at low frequency.
More specifically, the above-mentioned conventional bearing design includes a bellows made of resilient material forming a gas chamber and a hollow spherical throttling member which is connected to one of the bearing seats and divides the gas chamber bellows into two compartments. The bellows is fixed to the other bearing seat and has a metal insert in the region of the sliding surface of the throttling member. In the region of one of the compartments, the bellows, which is pneumatically sealed from the atmosphere, has a connection for an external gas supply which allows for the possibility of providing various spring constants by means of different pressures in the gas chamber. Since the bellows is suspended from the other bearing seat, it must assume the full force transmitted by the throttling member. Consequently, even if a gas supply for varying the spring constant is omitted, a continuous supply of gas is required since there is danger that the bellows, being subjected to high mechanical stresses, may not retain the required pneumatic seal, at least over long periods of time.